Polyphenyl thioether lubricating compositions

ABSTRACT

WHEREIN R&#34; IS AN ARYL GROUP OF FROM 6 TO 16 CARBON ATOMS, A HALOGEN SUBSTITUTED ARYL GROUP OF FROM 1 TO 16 CARBON ATOMS, AN ARYL SUBSTITUTED ARYL GROUP CONTAINING FROM 6 TO 16 CARBON ATOMS OR AN ALKYL GROUP CONTAINING 1 TO 12 CARBON ATOMS, R&#39;&#39;&#39;&#39;&#39;&#39; IS HYDROGEN OR AN R&#34; GROUP AND FROM 0.01 TO 0.5 PERCENT BY WEIGHT OF MONOCYCLIC, MONOHYDRIC ALKYL-SUBSTITUTED PHENOLS.   R&#34;-P(=O)(-H)-O-R&#34;&#39;&#39;   WHEREIN R IS A PHENYL GROUP OR A SUBSTITUTED PHENYL GROUP, R&#39;&#39; IS A PHENYLENE GROUP OR SUBSTITUTED PHENYLENE GROUP, IN WHICH THE SUBSTITUENTS ON SAID PHENYL AND PHENYLENE GROUPS ARE HALOGEN, ALKYL OR ALKOXY CONTAINING FROM 1 TO 4 CARBON ATOMS, N IS AN INTEGER OF FROM 1 TO 6, Y IS SULFUR OR OXYGEN PROVIDED THAT AT LEAST ONE OF THE GROUPS REPRESENTED BY Y IS SULFUR, AND MIXTURES OF SUCH THIOETHERS AND FROM ABOUT 0.05 TO ABOUT 1.0 PERCENT BY WEIGHT OF AN ORGANIC PHOSPHONIC ACID OF THE FORMULA   R-Y(R&#39;&#39;-Y)N-R   1. A LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF A POLYPHENYL THIOETHER HAVING THE FORMULA

US. Cl. 25246.7 2 Claims ABSTRACT OF THE DISCLOSURE Lubricating compositions comprising polyphenyl thioethers, polyphenyl ethers-thioethers or mixtures thereof and containing small amounts of a polar organic compound and an organic phosphinic acid or ester have improved lubricating properties. These compositions are useful as lubricants over Wide temperature ranges.

This is a division, of application Ser. No. 102,969, filed Dec. 30, 1970 (now US. Pat. 3,748,269 dated July 24, 1973).

IMPROVED POLYPHENYL THIOETHER LUBRICATING COMPOSITIONS This invention relates to improved lubricating compositions comprising polyphenyl thioethers, mixed polyphenyl ethers-thioethers and mixtures thereof, containing from 3 to 8 aromatic groups and a small amount of a polar organic compound and an organic phosphinic acid as lubricating additives.

Polyphenyl thioethers and polyphenyl ether-thioether combinations have found wide application as functional fluids due to their excellent thermal stability and lubricity. For example they have been found to be valuable as hydraulic fluids and as lubricants in motor operation, particularly in jet engines.

Development of synthetic base stocks such as the polyphenyl thioether has provided lubricant fluids which are useful at elevated temperatures such as 400 to 500 F. It is known that one of the aspects in which the polyphenyl thioether base stocks are considered deficient is in their lubricating characteristics, especially for steel on steel or on chrome anodized aluminum. These lubricating characteristics include the load-carrying abilities and wear properties, especially under conditions of pumping the lubricant where the pump contains a chrome anodized aluminum bearing surface or gear box. Thus there is a demand for additives for polyphenyl thioethers which additives will improve the lubricity of the polyphenyl thioethers for steel on steel or on chrome anodized aluminum surfaces.

An object of the present invention is to provide for improved lubricating compositions employing polyphenyl thioethers, polyphenyl ether-thioethers, or mixtures thereof as base stocks for applications where at least one of the surfaces to be lubricated is chrome anodized aluminum.

These and other objects will become evident upon consideration of the following specification and examples.

It has now been found that compositions consisting essentially of a major amount of a polyphenyl thioether base fluid having the formula wherein R is a phenyl group, an alkyl-substituted phenyl group wherein the alkyl group contains 1 to 4 carbon atoms, an alkoxy-substituted phenyl group wherein the alkoxy group contains 1 to 4 carbon atoms or a halogenated phenyl group wherein the halogen is bromine, fluorine or chlorine, R is a phenylene group, an alkyl or United States Patent Office- Patented Oct. 22, 1974 alkoxy-substituted phenylene group where the alkyl group contains 1 to 4 carbon atoms or a halogenated phenylene group wherein the halogen is fluorine, bromine or chlorine, and Y is selected from oxygen and sulfur but at least one of the Ys is sulfur and n is an integer having a value of from 1 to 6 and an additive amount of a polar organic compound and an organic phosphinic acid have unusual ability to lubricate steel on chrome anodized aluminum and steel on steel.

The amount of the polar organic compound employed in the compositions of this invention can range from 0.01 to about 0.5 percent by weight. It is preferred to employ the polar organic compound in the compositions of this invention in amounts of from 0.04 to 0.15 percent by weight based upon the total composition.

The amount of the organic phosphinic acid or ester employed in the compositions of this invention is from about 0.05 to about 1.0 percent by weight of the total composition. It is preferred to employ the organic phosphinic acid or ester in the compositions of this invention in amounts of from about 0.070 to about 0.2 percent by weight of the total composition.

The improvement in lubricity characteristics achieved by the addition of a perfluoro dibasic acid as the polar organic compound and the organic phosphinic acid or ester to the polyphenyl thioether base fluid is particularly unusual and surprising. Wear on a chrome anodized aluminum bearing surface is decreased at test temperatures of 200 F. whereas when the base fluid is tested without the additive the lubricity of the base fluid is not sufiicient and the bearing surface fails after a short time.

The polar organic compounds which are employed in the compositions of this invention include aliphatic perfiuoro dibasic acids, carboxy substituted polyphenyl thioethers, substituted phenols and aryl substituted fatty acids, acetylene dicarboxylic acids, aryl phosphates, and the like.

Illustrative of aliphatic perfluoro dibasic acids which can be employed in the compositions of this invention are the perfluorinated dibasic aliphatic acid containing from 3 to 10 carbon atoms and represented by the formula wherein n is an integer of from 1 to 8. It is particularly preferred to employ per-fiuorinated dibasic acid of formula II wherein n is an integer of from 2 to 6.

Illustrative of the carboxy substituted polyphenyl thioethers which are employed in the compositions of this invention are those having the formula (III) (RY-(R'Y) R) (COOH) wherein R, R', Y and n are as above-defined with the proviso that at least one Y is sulfur and that from one to two of R and R is substituted with a carboxy group and x is an integer of 1 or 2. Such carboxy substituted polyphenyl thioethers are for example m-(m-phenylmercaptophenylmercapto)benzoic acid, m-(phenylmercapto)benzoic acid,- o-(m-phenylmercapto)phenylmercapto-benzoic acid and the other carboxy substituted polyphenyl thioethers.

Illustrative of the substituted phenols which are useful in the compositions of this invention are the 2,6-(alkyl) phenols such as for example 2,6-di-t-butyl-4-methyl phenol and the like. It is preferred that the alkyl groups on the phenol contain from 1 to 12 carbon atoms.

Illustrative of the aryl substituted fatty acids which are useful in the compositions of this invention are those having the general formula ArC,H ,,-COOH wherein Ar is an aryl group containing from 6 to 16 carbon atoms and a is an integer of from 8 to 24. Illustrative of these aryl substituted fatty acids are, for example, phenyloctadecanoic acid, phenyloctanoic acid, tolyldodecanoic acid, xylyltetracosanoic acid and the like.

3 Illustrative of the acetylenic dibasic acids useful in the compositions of this invention are those having the general formula where b and c are integers of from to inclusive. Acetylene dicarboxylic acid is especially preferred for use in the compositions of this invention.

Illustrative of the aryl phosphate esters useful in the compositions of this invention are those having the formula wherein R is an aryl group containing from 6 to 16 carbon atoms and R and R are alkyl groups containing from 1 to 12 carbon atoms or an R group. It is preferred that when R R and R all represent aryl groups that at least one of the aryl groups be an alkyl substituted aryl group. Illustrative of the phosphate esters are for example, tricresyl phosphate, dibutyl phenyl phosphate, cresyl diphenyl phosphate, xylyl 'dicresyl phosphate, cresyl dioctyl phosphate and the like.

Illustrative of the perfluorinated dibasic acids represented by formula II are, for example, perfiuoro malonic acid, perfluoro succinic acid, perfluoro azelaic acid and penfiuoro sebacic acid.

The organic phosphinic acids or esters which are employed in the compositions of this invention are those of the formula wherein R" is an aryl group containing from 6 to 16 carbon atoms, a halogenated aryl group or an alkyl group containing from 1 to 12 carbon atoms, and R" is hydrogen or an R group. Illustrative of the groups represented by R" and 'R' are, for example, phenyl, tolyl, xylyl, naphthyl, a-methylmaphthyl and diphenyl, and such aryl groups substituted with halogen or with alkyl groups containing up to 10 carbon atoms. Further alkyl substituted aryl groups are nonylphenyl, ethylphenyl, butylphenyl, tbuty'lphenyl and the like. Such halogen substituted aryl groups are p-chlorophenyl, o-bromophenyl, m-fiuorophenyl, p-iodophenyl, chlo-rotolyl, bromoxylyl, chloronaphthyl, and the like. Illustrative of the alkyl groups represented by R" and R' are, for example, methyl, ethyl, propyl, isobutyl, pentyl, t-butyl, hexyl, isooctyl, nonyl, decyl, dodecy'l, and the like. Such aryl phosphinic acids are, for example, phenylphosphinic aci'd, nonylphenylphosphinic acid, tolylphosphinic acid, xylylphosphinic acid, naphthylphosphinic acid, diphenylphosphinic acid and the like. It is especially preferred to employ in the compositions of this invention compounds of formula III wherein R" is an aryl group and R' is hydrogen.

The polyphenyl thioethers employed in the composition of this invention have from 3 to 8 benzene rings and from 1 to 7 sulfur atoms with the sulfur atoms joining the benzene rings in chains as ether linkages.

By the term polyphenyl thioether as used herein is meant a compound or physical mixture of compounds represented by formula I. The term includes compounds wherein all of the Ys in formula I are sulfur. The term also includes those compounds which contain both oxygen and sulfur linkages between the benzene rings.

The compositions of this invention contain a major amount of the polyphenyl thioether base stock, i.e., at least 50 percent by weight of the total composition comprises a polyphenyl thioether. It is preferred that at least 60 percent by weight of the composition be a polyphenyl thioether base stock and even more preferred that at least 85 percent by weight of the total composition comprise a polyphenyl thioether.

The compositions of this invention can also contain from 0.01 to 10 percent by weight of the total composition of a dialkyl hydrogen phosphite extreme pressure additive. The dialkyl hydrogen phosphites useful are those wherein the alkyl groups contain from 1 to 12 carbon atoms. These alkyl groups are for example, methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, hexyl, decyl, isodecyl, dodecyl and the like.

Illustrative of the alkyl-substituents present in the phenyl and phenylene groups of the polyphenyl thioethers are for example, methyl, ethyl, propyl, 'butyl and the like. Illustrative of the alkoxy-substituents are, for example, methoxy, ethoxy, propoxy, butoxy and their isomers.

Illustrative of the polyphenyl thioethers which can be employed as base stocks for the compositions of this invention are the bis(phenylmercapto)benzenes. For example bis m-phenylmercapto benzene bis (o-phenylmercapto benzene bis (p-phenylmercapto benzene bis m-phenylmercaptophenyl) sulfide bis (o-phenylrnercaptophenyl) sulfide bis (p-phenylmercaptophenyl sulfide (rn-phenylrnercaptophenyl) (o-phenylmercaptophenyl) sulfide p-phenylmercapto-m-phenylmercapto diphenyl sulfide o-bis (o-phenylmercaptophenylmercapto benzene p-bis (p-phenylmercaptophenylmercapto benzene p-bis (o-phenylmercaptophenylmercapto benzene p-bis m-phenylmercaptophenylmercapto) benzene m-bis p-phenylmercaptophenylmercapto benzene o-bis (p-phenylmercaptophenylmercapto benzene and the like and mixtures thereof.

Illustrative of the mixed polyphenyl ether-thioether compounds which can be employed as base stocks in the compositions of this invention are for example,

o-phenylmercapto-m-phenoxy benzene p-phenylmercapto-o-phenoxy benzene m-phenoxy-p-phenylmercapto benzene o-phenylmercapto-p-phenoxydiphenyl sulfide o-phenylmercapto-m'-phenoxydiphenyl sulfide o-phenoxy-m-phenylmercaptodiphenyl sulfide m-phenoxy-p-phenylmercaptodiphenyl sulfide o-phenoxy-p-phenylmercaptodiphenyl sulfide p-phenoxy-p'-phenylmercaptodiphenyl sulfide o-phenoxy-o'-phenylmercaptodiphenyl sulfide o,o-bis(phenylmercapto diphenyl ether o-phenylrnercapto-m-phenylmercaptodiphenyl ether o-phenylmercapto-p-phenylmercaptodiphenyl ether m- (m-phenylmercaptophenylmercapto) (m-phenoxyphenylrnercapto) benzene [m- (m-phenylmercaptophenylmercapto phenyl] [m-(mphenoxyphenyl-rnercapto phenyl] sulfide 3- (m-phenylmercaptophenylmercapto -3 (tn-phenylmercaptophenoxy)diphenyl sulfide 3,3 this (m-phenylmercaptoph enylmercapto diphenyl et er 3- (rn-phenylmercaptophenylmercapto)-3'-(m-phenoxyphenoxy)diphenyl sulfide 4- (m-phenylmercaptophenylmercapto -4 m-phenylmercaptophenoxy)diphenyl ether 3- m-phenylmercaptophenylmercapto) -3 (m-phenoxyphenylmercapto)diphenyl ether 4,4-bis(m-phenylmercaptophenoxy)diphenyl sulfide 4,4'-bis (m-phenoxphenylymercapto diphenyl sulfide 3- (m-phenoxyphenylmercapto -3 (m-phenylmercaptophenoxy) diphenyl sulfide 3,3'-bis(m-phenylmercaptophenoxy)diphenyl ether 4- m-phenylmercaptophenylmerc apto -4'- (mphenoxy phenoxy)diphenyl ether 3-(p-phenylmercaptophenoxy)-3'-(p-phenoxyphenoxy) diphenyl sulfide 3- (m-phenylmercaptophenoxy) -3 (m-phenoxyphenyb mercapto) diphenyl ether 3,3'-bis(m-phenoxyphenylmercapto)diphenyl ether and 3- (m-phenoxyphenylmerc apto -3- (mphenoxyphenoxy) diphenyl sulfide.

In addition to the foregoing compounds, the phenyl and phenylene groups of such compounds can contain substituents, such as alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 4 carbon atoms and halogen such as chlorine, bromine and fluorine. Examples of such compounds are as follows:

4,4'-bis (m-tolylmercapto) diphenyl ether 3,3'-bis(m-tolylmercapto diphenyl ether 2,4'-bis (m-tolylmercapto) diphenyl ether 3,4'-bis (m-tolylmercapto diphenyl ether 3,3'-bis (p-tolylmercapto diphenyl ether 3,3-bis (xylylmercapto diphenyl ether 4,4'-bis (xylylmercapto diphenyl ether 3,4'-bis (xylylmercapto diphenyl ether 3,4-bis (m-isopropylphenylmercapto diphenyl ether 3,3-bis (m-isopropylphenylmercapto diphenyl ether 2,4-bis (m-isopropylphenylmercapto diphenyl ether 3,4'-bis (p-tert-butylphenylmercapto diphenyl ether 4,4'-bis(p-tert-butylphenylmercapto) diphenyl ether 3,3-bis (p-tert-butylphenylmercapto diphenyl ether 3,3 '-bis (2,4-di-tert-butylphenylrnercapto diphenyl ether 3,3'-bis( 3-chlorophenylrnercapto diphenyl ether 4,4'-bis 3-chlorophenylmercapto diphenyl ether 3 ,3 '-bis (m-trifluoromethylphenylmercapto diphenyl ether 4,4'-bis (m-trifluoromethylphenylmercapto) diphenyl ether 3,4'-bis (m-trifluoromethylphenylmercapto) diphenyl ether 2, 3 '-bis m-trifluoromethylphenylmercapto) diphenyl ether 3,3 -bis (p-trifluoromethylphenylmercapto diphenyl ether 3,3'-bis (o-trifiuoromethylphenylmercapto) diphenyl ether 3 ,3 '-bis (m-methoxyphenylmercapto diphenyl ether 3,4'-bis(m-isopropoxyphenylmercapto diphenyl ether 3 ,4'-bis (m-p erfluorobutylphenylmercapto) diphenyl ether 2- m-tolyloxy) -2'-phenylmercaptodiphenyl sulfide 2- (p-tolyloxy-3 '-phenylmercapto diphenyl sulfide 2- (o-tolyloxy -4'-phenylmercaptodiphenyl sulfide 3- (m-tolyloxy) -3'-phenylmercaptodiphenyl sulfide 3 m-tolyloxy -4'-phenylmercaptodiphenyl sulfide 4- (m-tolyloxy -4'-phenylmercaptodiphenyl sulfide 3-xylyloxy-4'-phenylmercaptodiphenyl sulfide 3-xylyloxy-3 '-phenylmercapto diphenyl sulfide 3-phenoxy-3'- (m-tolylmercapto diphenyl sulfide 3phenoxy-4'- (m-tolylmercapto diphenyl sulfide 2-phenoxy-3'- (p-tolylmercapto diphenyl sulfide 3 -phenoxy-4- (m-isopropylp henylmercapto) diphenyl sulfide 3-phenoxy-3'- (m-isopropylphenylmercapto diphenyl sulfide 3-m-toloxy-3 (m-isop ropylphenylmercapto diphenyl sulfide 4- (m-trifluoromethylphenoxy) -4-phenylmercaptodiphenyl sulfide 3- (m-trifluoromethylphenoxy) -4-phenylmercaptodiphenyl sulfide 2 (m-trifluoromethylphenoxy) -3 -phenylmercaptodiphenyl sulfide 3- m-trifluoromethylphenoxy-3 '-phenylmercaptodiphenyl sulfide 3 (p-chlorophenoxy) -3 '-phenylrnercaptodiphenyl sulfide 3- m-bromophenoxy) -4'-phenylmercaptodiphenyl sulfide bis [m- (m-chlorophenoxy) phenyl] sulfide m-bis 3- (p-methylphenylmercapto phenoxy] benzene m-bis [3 (m-trifluoromethylphenoxy) phenylmercapto] benzene m-bis 3- (m-bromophenoxy) phenylmercapto] benzene 3 ,3 '-?1i1s[m-(p-methylphenylmercapto)phenoxy]diphenyl su de 6 3,4'-bis[m- (p-methylphenylmercapto) phenoxy]diphenyl sulfide 3-(p-xenyloxy)-3'-phenylmercapto diphenyl sulfide,

and the like and mixtures thereof. It is also contempleted within the scope of this invention to employ mixtures of polyphenyl ether-thioethers as base stocks.

The compositions of this invention are useful as lubricants under extreme conditions. The compositions are especially useful for steel on chrome anodized aluminum lubrication.

The following examples serve to further illustrate the invention. All parts are parts by weight unless otherwise expressly set forth.

EXAMPLE 1 A polyphenyl thioether polyphenyl ether thioether lubricant composition is prepared by combining perfiuoro glutaric acid (0.1 gram) and phenylphosphinic acid (0.075 gram) with grams of a thioether of the following composition:

Percent by wt. meta-bis (phenylmercapto) benzene 50 bis phenoxyphenyl sulfide 12.5

(phenoxyphenyl) (phenylmercaptophenyl sulfide 23 .5 bis(phenylmercaptophenyl)sulfide 12.65 3 ring and 5 ring thioethers 1.35

This mixture is stirred for about 12 hours at 4045 C. After cooling to room temperature the mixture is filtered to remove a small amount of insoluble material.

The aluminum lubricity of the composition of Example 1 was shown using a chrome anodized oil pump. This is a Pratt & Whitney JT3D-3B main engine pump. This type of pump is commonly used in jet engine gear boxes. The gear box oil pump is a compound pump composed of the pressure oil pump and the gear box scavenge pump operating from a single shaft. Both drive gears of the pumps and the rotating shaft are hung from two outboard journals with a journal in the middle separating the two pumps. Rotating drive for both pumps is provided by a single axially located splined shaft which extends through one side of the pump housing to a power source. The driven or idle mating gears in these pumps rotate on a fixed shaft. The rotating shaft is steel, the case and journals are chrome anodized aluminum. Design loading is 50 p.s.i. for the pressure pump.

Normally, the journals are part of the pump case. For testing purposes, the housing is widened and chrome anodized bushings are placed between the shaft and the journal. Lubricity failure results from wear or seizure of the bushings. These are then replaced allowing continual testing with one pump.

A shock cycle test was used to evaluate fluids. The oil was circulated in the pump under no load while being heated to 200 F. The output of the pump was throttled until a discharge pressure of 20 p.s.i. was reached. This pressure was held for ten seconds, then lowered to zero p.s.i. for five seconds. This off-on shock cycle was repeated twenty times at 20 p.s.i., twenty times at 30 p.s.i., 40 p.s.i., 50 p.s.i., 60 p.s.i., and 75 p.s.i. This final load is 50 percent excess load above the design load. Completion of cycles without wear or seizure of the bushings constitutes a successful test.

The composition of Example 1 was able to complete 120 testing cycles without failure of the bushings. The base oil containing 0.1 percent diisopropyl hydrogen phosphite failed the test after 60 cycles. The base oil with only phenylphosphinic acid (0.1 percent) failed at 62 cycles. The thioethers containing only perfiuoroglutaric acid (0.08 percent) failed after 84 cycles.

The lubricating ability of the fluids of this invention was shown with a slow speed four ball machine. A slow speed four ball machine measures the boundary lubricity action of additives. This test is a variation of the well known Shell Four Ball Test in which a ball is rotated against three stationary balls. Wear scars and/or seizure loads measure additive lubricity. In the slow speed instrument the three stationary balls are replaced with circular discs. Standard operating conditions are:

3 kg. load 1 rpm. Room temperature to 700 F.

The speed of rotation is very low, namely one r.p.m. This equals 0.88 inches/minute. This is done for two reasons. It insures boundary conditions, i.e., metal to metal contact. It also eliminates metal skin temperature flashes which can occur at high speeds. Thus the bulk oil temperature is equivalent to the metal surface temperature. Under these conditions Wear is negligible and friction is used to follow lubrication. After covering the ball and disc with the test oil, the initial friction is recorded. The test sample is then heated to 700 F. with continuous recording of the friction. This gives a boundary fricnon-temperature profile for the experimental fluid over this temperature range.

From 200 to 700 F. the boundary friction on M50 steel for the blend from Example 1 was lower than that of the base stock containing only phenyl phosphinic acid. The friction lowering was greatest above 600 F. This temperature range corresponds to the metal skin temperature of bearing components at high temperature conditions.

EXAMPLE 2 To 100 grams of the base fluid of thioethers from Example 1 was added 0.075 gram phenylphosphinic acid and 0.05 gram of acetylene dicarboxylic acid. After heating at 45 C. for about twenty hours, the blend was cooled to room temperature and filtered.

A boundary friction-temperature curve for the fluid from Example 2 was run on M50 steel. The boundary friction for the blend was significantly lowered relative to the base stock containing only phenylphosphinic acid over a temperature range of 400 to 700 F.

EXAMPLE 3 To 100 grams of the base fluid of the thioethers as set forth in Example 1 was added 0.075 gram phenylphosphinic acid and 0.05 gram of m (m phenylrnercaptophenylmercapto)benzoid acid. After heating at 45 for about twenty hours, the blend was cooled to room temperature and filtered.

A boundary friction-temperature curve for the fluid from Example 3 was run on M50 steel. The boundary friction for the blend from 500 to 700 F. was significantly lower than a blend containing only phenylphosphinic acid.

EXAMPLE 4 To 100 grams of the base fluid of thioethers from Example 1 was added 0.075 gram phenylphosphinic acid and 0.05 gram of 2,6-di-t-butyl-4-methyl phenol. After heating at 45 C. for about three hours the blend was cooled to room temperature and filtered.

A boundary friction-temperature curve for the fluid from Example 4 was run on M50 steel. The boundary friction for the blend was either significantly lower than, or equal to the bounary friction of the base stock containing only phenylphosphinic acid over a temperature range of from room temperature to 700 F. From 500 F. to 700 F. the boundary friction of the blend of Example 4 was significantly lower than that of the blend containing only phenylphosphinic acid.

8 EXAMPLE 5 To grams of the base fluid of thioethers from Example 1 was added 0.075 gram phenylphosphinic acid and 0.05 gram of tricresylphosphate. After heating at 40 to 45 C. for about 3 hours the blend was cooled to room temperature and filtered.

A boundary friction-temperature curve for the fluid from Example 5 was run on M50 steel. The boundary friction for the blend was lower than for a base stock containing only the phenylphosphinic acid over a temperature range of from room temperature to 700 F.

EXAMPLE 6 To 100 grams of the base fluid of thioethers from Example 1 was added 0.075 gram phenylphosphinic acid and 0.05 gram of phenyloctadecanoic. After heating at 40 to 45 C. for about 3 hours the blend was cooled to room temperature.

A boundary friction-temperature curve for the fluid from Example 6 was run on M50 steel. The boundary friction for the blend was lower than for a base stock containing only the phenylphosphinic acid over a temperature range of from 600 to 700 F.

It will be appreciated that the composition of the invention, in addition to the polyphenyl thioether base fluid and the organic phosphinic acid additive, may also contain other additives, such as oxidation inhibitors, rust and corrosion inhibitors, antifoaming agents, detergents, viscosity index improvers such as polymeric materials for example, polyacrylate alkyl esters, polymethacrylate alkyl esters, polyoxyalkylene compounds, polyurethanes and the like. Such additives are usually employed in amounts as low as 10 parts per million for antifoaming agent to as much as 15 parts by weight of the total compositions for viscosity index improvers.

While this invention has been described with respect to various specific examples and embodiments, it is understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims.

The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:

1. A lubricant composition consisting essentially of a major amount of a polyphenyl thioether having the formula wherein R is a phenyl group or a substituted phenyl group, R is a phenylene group or substituted phenylene group, in which the substituents on said phenyl and phenylene groups are halogen, alkyl or alkoxy containing from 1 to 4 carbon atoms, n is an integer of from 1 to 6, Y is sulfur or oxygen provided that at least one of the groups represented by Y is sulfur, and mixtures of such thioethers and from about 0.05 to about 1.0 percent by weight of an organic phosphinic acid of the formula wherein R" is an aryl group of from 6 to 16 carbon atoms, a halogen substituted aryl group of from 6 to 16 carbon atoms, an alkyl substituted aryl group containing from 6 to 16 carbon atoms or an alkyl group containing 1 to 12 carbon atoms, R' is hydrogen or an R" group and from 0.01 to 0.5 percent by weight of monocyclic, monohydric alkyl-substituted phenols.

2. A composition of Claim 1 wherein the substituted 2,274,291 2/1942 Clayton et a1. 252498 phenol is 2,6-di-t-butyl-4-methylphenol. 2,202,877 6/1940 Stevens et a1. 25252 R References Cited FOREIGN UNITED STATES PATENTS 851,651 10/1960 Great Brltam 252-52 R 3,311,665 3/1967 Campbell et a1. 2524S X W. H. CANNON, Primary Examiner 2,197,833 4/1940 'Reiff 252-42.7

2,730,499 1/ 1956 'Pokorny 25249.8 US. Cl. X.R.

2,174,019 9/1939 Sullivan 252-498 252-465, 49.8

P0405) UNITED STATES PATENT OFFIQE I CERTIFICATE OF CORRECTEON grail N- w' fl Dated Oct. 22, 1974 Inventor-(s) Frank rk V It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 25, delete the word "IMPROVED" from the subtitle.

Column 2, line 56, 1"0-(m-phenylmercapto)phenylmercapto-benzoic" should be 0- (m-phenylmercaptophenylmeroapto)benzoic Column 3, line 4,. formula reads "HOCC-C H -C=-CC H COOH" shoul'cl'be HOOC--C H C CC H -COOH Column 7, line ,50, ."benzoid" should be benzoio Column 7, line '69, "bounary" should be boundary Signed and sealed this 18th day of February 1975.

(SEAL) Attest:

. c. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks 

1. A LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF A POLYPHENYL THIOETHER HAVING THE FORMULA 